There has been known a power supply device configured to store a plurality of battery modules (each including a plurality of batteries connected in series) in a battery case and to protect the battery modules by use of a protective electronic circuit installed in the battery case (see Patent Literature 1, for example). In the power supply device described in the Patent Literature 1, bus bars connecting the battery modules together are connected to the protective electronic circuit in order to detect the voltages of the battery modules. For the connection of the bus bars to the protective electronic circuit, each bus bar is connected to a fuse via a lead plate, and the fuse is connected to the protective electronic circuit via a lead wire.